The actual incidences, fatality rates, geographic distribution, and loss of economic productivity, and etiologies of acute vector-borne viral and rickettsial diseases are poorly quantified and elucidated owing to inadequate dissemination and application of the scientific methods of arbovirology, rickettsiology, and vector biology. The proposed program for the study of emerging and re-emerging vector-borne viral and rickettsial diseases in the tropics of Latin America comprises five institutions involving two Mexican universities, a Cameroonian university, and universities in Texas and Colorado. The goal is to develop the scientific level at the Universidad Autonoma de Nuevo Leon (Monterrey, Mexico) and the Universidad Autonoma de Yucatan (Merida, Mexico) to that of international competitiveness for independent research support and to build upon the foundation established by the previous Fogarty project in Cameroon (University of Buea). Acute febrile illnesses in Cameroon include many cases of Rickettsia africae infection, chikungunya and flaviviral infections. It is an outstanding opportunity to determine the risk factors for severity of rickettsial disease, to elucidate the vector biology of R. africae, to identify African human ehrlichioses, and to determine the ecology of sylvatic dengue and other arboviruses and to identify and characterize emerging infections in general in west central Africa. The studies will enhance knowledge of West Nile virus, Venezuelan equine encephalitis virus, other arboviruses, typhus, murine typhus, R. felis infections, and human ehrlichiosis in all parts of Mexico.